That’s according to a study from Boston College’s Center for Retirement Research that shows fewer than half of US workers will have enough money saved to retire at 65. But if those same people keep working until they are 70, the picture improves dramatically, with 86 percent likely to be financially comfortable in retirement.

“The 401(k) system has worked for some, but it has not worked for many,’’ said Anthony Webb, research economist and an author of the study. To have more time to save and to maximize Social Security benefits, he noted, “One of the most powerful levers is working longer.”

At 57, Joyce Wilkins, a nurse at Morton Hospital in Taunton for 30 years, wishes she could afford to retire now. She enjoys her job but also is also caring for her elderly mother and helping with her own grandchildren. Though she has a pension, she figures she will have to work until she is 66, the age at which Social Security pays full retirement benefits.

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“By the time I’m at an age where they would let me retire, I will have been working almost 50 years,’’ Wilkins said. “I’d like to travel, I’d like to enjoy my grandchildren, I’d like to enjoy my health.”

The study takes into account 401(k) retirement plans and pensions, as well as home values, all of which have suffered in the economic downturn. And Social Security weighs heavily in the calculation, because the benefits are so much greater for those who wait until at least 66 — and even better, 70 — instead of cashing in at 62.

Assume the average person needs about 75 percent of his or her annual income to be comfortable in retirement.

The average 55- to 64-year-old has a 401(k) balance of less than $100,000, Webb said.

That will provide only $5,000 a year, over a 20-year retirement. So Social Security has to make up the difference.

A worker making $65,000 a year would get $1,236 a month if he retired at 62; waiting until age 70 turns that check into $2,253 monthly.

For some, the BC study may bring a bit of relief — you will have to work longer, but not forever. Baby boomers who grew up believing they could drop into a chaise longue promptly at 65 may find the idea of having to work longer deeply disappointing. However, others, as long as they are healthy, want to be productive as they get older, and don’t want to be idle for a decade or two.

Take Josef Porteleki, owner of Roslindale Hardware, where he has worked for 45 years. He’s 65 and has no interest in retiring any time soon. But he is hoping to spend a bit more of his time on his other vocation, playing violin with the Newton Symphony Orchestra and other ensembles.

“I enjoy working. I enjoy what I do,’’ Porteleki said during a rare lull in the stream of customers to his busy neighborhood store. Having come to this country in his teens from Austria, Porteleki always felt that hard work could pay off, he said, and he has been able to save for retirement. But, he said, “It doesn’t mean a guarantee. It means you have an opportunity.”

His son, Alex, sees things a bit differently at age 36. Owning a business is a sometimes grueling, seven-day-a-week job, he said. And while he hopes to one day enjoy a healthy retirement, after a full career and raising two sons, “It’s so far in the future, I can’t really even speculate,’’ he said.

But today’s younger workers are the ones most likely to have to delay retirement. According to the study, the older you are right now, the greater the chance you will have enough money to retire at an earlier age. For instance, people 50 to 59 are twice as likely to be able to afford to retire at 62 as those who are currently 30 to 39.

That’s in part because many older workers enjoy traditional pension plans, which are being phased out at many companies. They also may have done better in their IRAs or 401(k) plans, having invested more aggressively in better markets and more conservatively in recent years.

But not everyone wants to work longer. For people with demanding physical jobs, such as in construction or nursing, the prospect of working to age 70 may not be possible, or reasonable, said Russ Davis, executive director of Massachusetts Jobs With Justice, an advocacy group for workers’ rights.

“If people want to work longer — certainly people are living longer and are more vigorous — they should be able to,’’ he said. “There are a lot of physically demanding jobs in which it’s totally unreasonable for people to have to work until they’re 70.’’

Webb, the economist, concurs. “I would not want to go to West Virginia and go into a bar and tell coal miners, look it’s in your interest to work until 70,’’ he said.

Aida Deng, a 50-year-old accountant who lives in Quincy, said she thinks the ideal retirement age would be 59 or 60. Americans work too hard and have to worry too much, she said, compared to 25 years ago, when she moved here from China. She also worries that opportunities for young people will be hurt by older workers staying on the job longer.

“The older people work, and the young people are home with nothing to do,’’ Deng said.

Webb dismisses that theory, saying a healthy economy should produce plenty of jobs, and that studies have shown older workers do not take positions away from younger people.

For Webb, there is a bright side to his study: It dispels the notion that we will have to work forever. “You get all these horror stories,’’ he said. While most people can’t afford to retire early, he said, “it’s not true that they have to work until they are 80.”

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